MPEG video encoding using depth from focus

When a picture is compressed in MPEG video, image quality of important regions is maintained without changing the total amount of information; this is done by assigning a high information priority to the important region. Therefore, we propose a method to modify a quantizer scale according to the importance estimated according to a quantity for the depth of focus. Image quality of an important region is not deteriorated much even if the total amount of information is decreased. Moreover, in television broadcasting, subtitles are usually in focus, so the proposed method can extract subtitle regions and give more priority to them.